What are Different Types of Seashells?

Shells (bèi ké) are the outer shells of mollusks that live near the water. They are formed by secretions of a special glandular cell of mollusks to protect the soft parts of the body. Compared with natural calcium carbonate minerals in nature, shells have a unique multi-scale, multi-level "brick-mud" assembly structure, and because of their multi-level layered structure, they have good toughness and high strength ^[2] .

Studies have found that the formation of shells is a biomineralization process that uses a small amount of organic macromolecules as

Shell mechanical properties and utilization

The mechanical properties of a shell are a macro manifestation of the interaction between the hard attributes of the macrostructure and the auxiliary attributes of the microstructure. The research found that the internal structure of pearl layer is similar to human bone. It is a wafer-like structure formed by organic matter interconnecting nano-scale granular inorganic minerals, forming a bridge-like structure of organic matter and inorganic matter, which is a pearl layer structure with good mechanical properties. . The mechanical properties of shells are mainly affected by crack deflection, fiber pull-out, and organic bridging. It is under the synergistic effect of multiple factors and dimensions that shells show good mechanical properties. Therefore, a full understanding of the mechanical properties of shells and their products is helpful to the development of advanced shell crafts and shell powder-based building materials ^[3] .

Shell optical characteristics and utilization

The optical characteristics of the shell are mainly due to the microstructure of the shell on light reflection, interference, diffraction, and absorption characteristics of the characteristic spectrum. Diffraction of light by the thin layer of the pearl layer involves diffraction of light by the slits between the layers and between the aragonite platelets. The change is also related to the size, morphology and arrangement of aragonite crystals in the pearl layer. The inner surface of the shell has a aragonite structure mainly composed of calcium carbonate and a small amount of organic components. They have characteristic absorption peaks in a certain spectral region. Therefore, a full understanding of the optical properties of shells and their products is helpful for the research of shell product detection ^[3] .

Shell adsorption characteristics and utilization

Shell adsorption characteristics are due to its relatively loose structure, relatively large pore diameter, and wide and uniform pore distribution; the surface of shell powder is large and the adsorption efficiency is high. Can realize the removal of crude oil, heavy metals, sulfur, dyes, pesticide fungicides, etc. Shell powder can be used as a catalyst carrier to adsorb crude oil. The catalyst is supported on the larger reaction area on the surface of the shell powder, which increases the contact area between itself and the oil on the sea surface and improves the reaction efficiency of the catalytic adsorption reaction. Shells can be used in the field of water treatment. Using shells as a calcium source for hydroxyapatite can adsorb and remove many metals in wastewater. The product of the shell after combustion can be used for desulfurization treatment. Because more pore surfaces inside the particles participate in the desulfurization reaction, the pores are not easily blocked by the desulfurization products during the reaction, and a more complete desulfurization reaction can be performed. In addition, using this feature, shell powder can also be used in water treatment, dyes, pesticide residue treatment and other fields ^[3] .

Shell biocompatibility and utilization

The biocompatibility of shells is mainly based on bioactive components of organic matter. Studies have found that there are signal molecules in the shell organic matrix that can promote cell osteogenic differentiation. These signal factors can activate the activity of cell alkaline phosphatase and promote the expression of certain specific proteins and genes during the process of cell osteogenic differentiation. Cell body mineralization, etc., therefore, nacre shows good biocompatibility in the in vivo environment. It was found that human bone marrow stromal cells grow and secrete cell matrix on nacreous human bone material, and pearl layer-polylactic acid composite artificial bone material has no significant effect on the increase of bone marrow stromal cells, showing good biocompatibility. Therefore, based on the biocompatibility of shells, it can be used for the research of shell-based biomaterials ^[3] .

Shell biological activity and utilization

Studies have shown that shells contain a variety of biologically active ingredients. On the one hand, these components have good biological activity on the one hand, and on the other hand, their microstructures have changed during the processing and extraction process, which has stimulated their biological activity. The research found that the active calcium oxide prepared from scallop shells has better activity and more obvious antibacterial effect than ordinary calcium oxide. The bioactive material hydroxyapatite was prepared from discarded shells. The water bath heating method was used, and shell powder was used as the raw material. With diammonium hydrogen phosphate as the phosphorus source and urea as the additive, the nano-ribbon hydroxyapatite with high purity and uniform size controllable was successfully prepared; the shell was immersed in phosphate buffer solution for 24 hours, and then dissolved-re- The crystallization reaction deposits a layer of carbonate-type apatite with a flaky structure on the surface of the shell. The results show that the prepared apatite has excellent in vitro biological activity; therefore, the biological activity based on the shell and its components can be used for Research on shell-based biomaterials and bioactive substances. In addition, starting from the shell structure, the current domestic and foreign shell waste utilization technologies are summarized; the advantages of shell powder and light calcium carbonate in improving the strength and handwriting performance of handsheets are compared and analyzed; It has a certain medicinal value and can be used for the treatment of diseases; using the Philippine clam shell powder as a raw material to prepare environmentally-friendly snowmelting agents ^[3] .